I'd wait to hear more information. Melamine seems to be a very commonly-used resin used in many gluing and particle-board pre-fab wood applications. If it was lethal in small amounts, nobody at Ikea would be alive today. The wide range of uses creates many paths of unwitting contamination.

Does this mean the pesticide analysis was wrong, or did they find both things?

There are a large number of chemical companies, some in China, that manufacture both fertilizers and melamine, which apparently have a lot of chemical precursors in common.

This is highly unlikely to be any form of deliberate sabotage.